Manage your subscription

Ediacarans: the ‘long fuse’ of the Cambrian explosion?

By James O'Donoghue

A FERN-LIKE impression appears in the rock face. Grasping at their rope, the boys very nearly miss it. It is April 1957 and three schoolboys are climbing in a quarry in Charnwood Forest in the English east midlands. Incredible as it would have seemed at the time, this serendipitous find was about to change our understanding of the history of life.

“Our reaction was, it’s a leaf,” says Roger Mason, who was 16 when he discovered the fossil and is now a professor at the China University of Geosciences in Wuhan. “We were surprised, but I didn’t know enough about geology to realise how startling a discovery it was.” A few days later he persuaded Trevor Ford of the nearby University of Leicester to have a look. Ford was sceptical. The Charnwood rocks were Precambrian, too old for fossils. Everyone knew that. But Ford was astonished at what he saw. The find was clearly a fossil resembling a fern frond about 20 centimetres long.

To understand the significance of finding a fossil like this in Precambrian rocks, you have to go back to the time of Charles Darwin. He was familiar with the mystery of the “Cambrian explosion” – the abrupt appearance in the fossil record of multicellular animals 542 million years ago. How could such diversity be seen in the Cambrian but not before? In 1859, Darwin wrote in On the Origin of Species that the Precambrian must have “swarmed with living creatures” that had not been preserved. The problem became known as Darwin’s dilemma and remained a puzzle for nearly a century.